Semi-automatic threading-device for sliding lathes



Jan- 15, 1962 M. GARoMBo 3,016,777

SEMI-AUTOMATIC THREADING-DEVICE FOR SLIDING LATHES Filed Oct. 28. 1954 y l i F75 1f 1T?" "Wh f 4 ad a i HLP L U- L11-:Q 21:53:: 2:: Ill Fg-fla 3;;

United States Patent Office 3,016,777 Patented Jan.`16, 1952 3,016,777 SEM-AUTOMATIC THREADING-DEVICE FOR SLIDING LATHES Michele Garornbo, Piazza Rebaudengo 22, Turin, Italy Filed st. 28, 1954, Ser. No. 465,387 Claims priority, application Italy Nov. 10, 1953 1 Claim. (Cl. 82-5) The object of the present invention is to provide a semiautomatic threading-device for sliding lathes.

This device is essentially characterized by the fact that the pitch of the thread is generated by a feed cam driven by the feed rod of the lathe through artelescopic transmission and universal joints acting on the longitudinal secondary tool carriage against return springs which automatically drive back said carriage in i-ts starting position when the carriage has reached the end of its working travel, and a return cam is coaxial to the first cam and rotating with the same drives back the tool from the work-piece at the end of its working-travel against return springs acting on the transversal secondary carriage and automatically approaches the tool to the work-piece at the beginning of the next working-travel, the transversal feed being given by hand by the operator.

The annexed drawing illustrates the object of the present invention by a form of execution given as a merely indicative and not limitative instance.

FIGURE l schematically shows a device according to the invention in plan, mounted on a sliding lathe;

FIGURE 2 shows the same in side elevation;

FIGURE 3 is a partially sectioned plan view of the device on a larger scale;

FIGURE 4 shows the device in side elevation, partially sectioned on line lV-IV of FIGURE 3;

FIGURE 5 is a transversal section of the device on line V-V of FIGURE 3.

With reference to FIGURES 1 and 2, 1 indicates the longitudinal rod of the lathe, driven by the conventional gear box and having at its outer end a back gear 2 driving in turn a telescopic transmission 3 with universal joints connected with the threading-device 4 mounted on the transversal carriage 5 of the lathe.

The end 3a of the telescopic transmission transmits the motion of the rod onto a worm gear 6 being a part of the threading-device 4 and meshing with a tooth wheel 7 enclosed in a box S and journalled in 9 on ball bearings 10 mounted in said box 8.

On the journal 9 are connected a return cam 11 and a feed cam 12 for the tool carriage. ln the example shown cam 11 is placed within the box 8, directly above the tooth Wheel 7, while cam 12 is connected on the projecting end of journal 9 and fixed on this journal by a screw 13. By this way cam 12 m-ay be easily changed with another cam having a different form and different size.

The tool return earn acts onto the curved end of a flat lever 14 which may rotate on a fixed pivot 14a, which lever enters box 8 through a slide slot. The other end of lever 14 enters through a corresponding slot the base 15 of the transversal tool carriage and -acts upon a plug 16 fixed to the lower portion of the tool carriage 17 which may slide on base 15. A series of pressure springs 18 against plate 19 screwed on base 15 to push carriage 17 in the direction of arrow A (FIG. 3), so ensuring a continuous engagement between the inner end of lever .14 and the return cam 11.

The feed cam 12 which moves the longitudinal secondary carriage acts upon the end of a rod 20 which is firmly fixed on said carriage 15. The touch between rod 2i) and cam 12 is ensured by a series of pressure springs 21, each of which surrounds a tie rod 22 freely passing through box 8. The inner end of said rod 22 is lirmly fixed, i.e. screwed on carriage 15 whilst the outer end of said rods bear an adjustable nut 23. The ends of springs 21 engage against one side with the inner portion of box 8 turned in direction of the carriage and on the other side with the adjustable nuts 23.

The device acts as follows: After having mounted on the mandrel the work-piece to be threaded and fixed the return gear 2 and cam 12 according to the length of the thread to be cut, the main carriage of the lathe shall be brought in its working position and fixed on the bed. The telescopic transmission 3 with universal joints ensures a constant contact between the threading device 4 and the feed shaft or rod -1 in any position in which the main carriage and the cross slide or secondary carriage are placed.

When the lathe has been started, tooth wheel 7 will rotate with a speed according to the gear ratio of the gear box and of the return gear 2 connected with rod 1 and moreover according to the fix-ed ratio between worm 6 and gear wheel 7.

Cam 12, rightly moulded, will rotate clockwise with tooth wheel 7 and give the longitudinal feeding motion to the tool on the work-piece at a pitch which is governed by the rotating speed of cam 12 and therefore by the speed of the longitudinal feeding motion of the tool. During the tool cutting operation the cylindrical part of restoring cam 11 will slide against the inner side of the restoring lever 14 without operating it, and thus maintain the point of the tool in the required position for effective cutting, due to the pressure exerted by springs 18. As soon as the root of the nose 12a of cam 12 is in line with rod 20, that is at the end of the working-travel, the nose 11a of cam 11 will be in line with the end of return lever 14 and swing said lever round its pivot 14a and drive back the tool from the worlopiece. lBy pursuing the rotating motion of both cams, -rod 20 will slide on the `concave portion of cam 12 and the springs 21 will retract the tool-carriage while lever 14 slides on the nose 11a of cam 11 holding the tool back from the work-piece. As soon as rod 20 has ended its sliding motion on the concave portion of cam 12 for beginning its working-travel again, the inner end of return lever 14 will end its sliding motion on the nose 11a of cam 11 and the tool will return in its starting position under the action of the springs 18 in touch with the work-piece. At this instant, or also during the return operation, the operator can attend by hand to the transverse advancement of the tool in readiness for the next cutting operation.

In this way there has been provided a semi-automatic threading-device in which the travels of the tool are fully automatic, without stopping or inverting the motion of the lathe, the operator only ought to provide to the transversal feed of the tool by beginning of each workingtravel.

The transversal carriage may obviously be provided with an adjustable stop for limiting the depth of the thread to be cut.

The device described may be used as well for internal as for external threads.

Structural details, materials, form and the like of the threading-device according to the present invention may anyhow vary from what is described and disclosed as an instance without departing from the invention principles.

Having so described my invention, I state that what I wish to claim is as follows:

A threading attachment for a lathe, comprising, a base adapted for fixation to the slide of the lathe and including a casing integrally connected therewith, a longitudinal slide mounted on said base for guided translation thereon parallel with the axis of rotation of a workpiece mounted between centers in the lathe, first spring means acting between said base and said longitudinal slide, urging the latter into retrograde translation along said axis, a toolcarrying cross slide mounted on said longitudinal slide for guided translation thereon toward and from said axis, second spring means between said slides and urging said cross slide toward said axis, a vertical shaft journaled in said casing for rotation on an axis iixed with said base, and having a free end projecting upwardly throughan aperture in said casing, a retraction cam fixed to said shaft Within said casing, a feed cam removably fixed to the free end of said shaft above and externally of said casing, a lever pivoted between its ends on said hase, one end of said lever projecting through an aperture in said casing to engage said retraction cam, the other end of said lever slidably engaging an abutment on said cross slide, a cam follower lixed with said longitudinal slide and engaging said feed cam, a worm gear fixed with said shaft within said casing, a worm journaled on said base and in mesh with said worm gear, and means rotating said worm in timed relation with rotation of the workpiece between lathe centers, said retraction cam operating said lever to 4 retract said cross slide from said axis, just prior to completion of a work stroke translation of said longitudinal slide along said axis.

References Cited in the file of this patent UNITED STATES PATENTS 1,454,554 Mitchell May 8, 1923 1,798,143 Dardelet Mar. 3, 1931 2,176,676 Lupo Oct. 17, 1939 2,291,591 Medholdt July 28, 1942 2,511,196 Cuttat June 13, 195() 2,566,116 Chang Aug, 28, 1951 2,584,629 Smith Feb. 5, 1952 2,590,224 Armstrong Mar. 25, 1952 `2,660,737 Escure Dec. l, 1953 FOREIGN PATENTS 16,021 Great Bri-tain 1893 96,506 Switzerland May 20, 1921 398,716 France June 12, 1909 449,787 Italy June 30, 1949 561,727 Great Britain June 1, 1944 

